Construction of towers for support of various items has been practiced for many years. Various towers of various materials, including wooden, steel, and, more recently, concrete, have been provided to support, for example, electrical transmission lines. In like manner, wind driven apparatus including windmills and wind-driven power generators in various forms and designed for many purposes (including for example pumping of water from wells as well as, more recently, generation of electrical power) have also been developed.
Various apparatus are known and utilized in the tower construction and support arts to stabilize the tower structures. For example, post-tensioning devices are disclosed in Zavitz et al. (U.S. Pat. App. Pub. No. 2009/0307998), Zavitz et al. (U.S. Pat. App. Pub. No. 2009/0308006), and Knox et al. (U.S. Pat. App. Pub. No. 2009/0308019). Further examples of post-tensioning devices include Dietrich (U.S. Pat. No. 3,950,840) (disclosing a method of anchoring a ring tensioning member in a circular container); Alper et al. (U.S. Pat. No. 4,075,801) (disclosing storage tanks with walls that are prestressed by tensioned tendons disposed on the periphery thereof); Siegfried et al. (U.S. Pat. No. 5,066,167) (disclosing a prestressed concrete lining in a pressure tunnel); Siegfried et al. (U.S. Pat. No. 5,180,253) (disclosing an arrangement of prestressing tendons in a pressure tunnel); and Grossman (U.S. Pat. No. 6,588,160) (disclosing a composite structural member with pre-compression assembly).
The subject matter of each of the herein-referenced published patent-related documents is fully incorporated herein by reference, and for all purposes.
One approach to forming a tower structure is to utilize pre-cast components (such as legs or staves). These components are assembled together to form the tower structure, and post-tensioning devices and filler materials are utilized to secure the components together. However, presently known post-tensioning devices and filler materials utilized in the tower construction and support arts have a variety of disadvantages.
For example, many known post-tensioning devices, while generally providing stabilizing forces to tower structures, are entirely or substantially disposed in conduits defined internally by or placed/residing in the structural components of the tower structures. Thus, such known post-tensioning devices are difficult to initially install and join together for post-tensioning, and are also difficult to inspect. Further, because the conduits in the structural components typically are defined through a substantial portion of the width or length of the structural components, the structural components are difficult to fabricate.
Further, typically filler materials are difficult, time-consuming and expensive to utilize during construction of a tower structure. For example, typical grout materials that are utilized in tower structure construction applications require the use of extensive formwork to contain the grout while the grout is curing. Further, typical grout materials for tower structure applications, if not installed correctly, may not provide the desired structural support due to the existence of air bubbles and other defects. Additionally, the use of known post-tensioning devices and filler materials together is exceedingly difficult, due to the inability to access the post-tensioning devices as discussed above and combined with the use of a filler material that may further impede access to the post-tensioning devices. Thus, the stabilizing and structural advantages potentially provided by the post-tensioning devices and filler materials may in many cases not be fully realized.
Accordingly, improved methods and apparatus for assembling tower structures are desired in the art. In particular, improved filler materials for use in the assembly of tower structures would be advantageous. Such improved filler materials would be further particularly advantageous in combination with, for example, post-tensioning devices, and related methodology that are easy to install and inspect.